Save the file under the components directory of foobar2000 (e.g. C:\Program Files\foobar2000\components) and restart the program. There will be a new item added under the Playback menu. Select the format of info that you want to show on MSN. Also remember to turn on the "Show what I'm listening to" feature on your MSN Messenger.

The C++ source code is also available. You will need to download the foobar2000 SDK in order to build it.